Transmission for a working vehicle

ABSTRACT

A transmission for a working vehicle like a tractor of the invention is housed in a transmission housing 1 interposed between an engine and a rear axle housing 2. An interior of transmission housing 1 is divided into a front chamber A and a rear chamber B through a partition wall 1a. In front chamber A is disposed a main-clutch system partition centering a traveling-input shaft 7. In rear chamber B is disposed a speed-changing system as a combination of reversing arrangement and multi-speed-changing arrangement. In a rear opening of housing 1 is disposed a bearing plate 3. In rear chamber B, a first speed-changing shaft 8, a second speed-changing shaft 9 and a front transmission output shaft 10 are supported in parallel between wall 1a and plate 3. A regular speed-reduction gear train and a reversing speed-reduction gear train are interposed between shafts 8 and 9, so that shafts 8 and 9 can be connected with each other through one of the gear trains by a first clutch device C1 on shaft 8. A second clutch device C2 is on shaft 9 so as to selectively connect shafts 7 and 9 directly. A plurality of gear trains for multi-speed stages are interposed between shafts 9 and 10, so that shafts 9 and 10 are connected with each other through one of the gear trans by a third clutch device C3 on shaft 10. A cover 51 is settled on housing 1. A main (second) speed-changing lever 52 and a sub (first) speed-changing lever 52 are disposed respectively at both lateral sides of cover 51. Third clutch device C3 is operated by lever 52. First and second clutch devices C1 and C2 are selectively operated by lever 55.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a construction of a transmissionadapted to a working vehicle like a tractor for transmitting power froman engine of the vehicle into a differential unit for rear wheelsthereof, particularly, of a type having a travelling-input shaftdrivingly connected with the engine and a travelling-output shaftdrivingly connected with the differential unit, which are disposed inparallel to each other, and it relates to a construction of a housingfor the transmission. Additionally, it relates to various systems inconnection with the transmission, particularly, a speed-changingoperation system (occasionally having a creeping speed range), whichincludes a supporting mechanism of a lever for speed-changing and aconnecting and disconnecting mechanism of the speed-changing operationsystem to the transmission.

2. Related Art

A transmission of a working vehicle like a tractor includes a series ofa main-clutch system and a speed-changing system between an output areaof an engine mounted on a front portion of the vehicle and adifferential unit for rear wheels housed in a rear axle housingsupporting rear axles. Conventionally, the main-clutch system is housedin a clutch housing as a front part housing continuously connected tothe output portion of the engine, and the speed-changing system ishoused in an exclusive transmission casing as a middle part housinginterposed between the front part housing and the rear axle housing as arear part housing. The transmission casing is fastened at its front andrear ends to both of the housings by bolts. The main-clutch system andthe speed-changing system are connected with each other according tofastening the clutch housing and the transmission casing.

Also, the conventional speed-changing system housed in the transmissioncasing has reversing arrangement and tandem speed-changing arrangementsdistributively disposed on a shaft as described in Japanese Patent No.Hei 5-26686.

Also, the conventional transmission casing has respective supportingportions for a plurality of speed-changing levers as described inJapanese Utility Model No. Hei 6-3213.

Japanese Patent Nos. Hei 5-26686 and Hei 7-117507 describe a front-wheeldriving PTO (power-take off) system for transmitting power from thespeed-changing system in the transmission casing to the front wheels.Particularly, the former describes a front-wheel driving PTO unitoutwardly projecting from the transmission casing. A transmission shaftconnecting the unit and the speed-changing system is disposed outsidethe transmission casing.

It is desirable to reduce the manufacturing cost of the transmission andto simplify its assembly and maintenance. However, the conventionalhousing for the transmission consists of the above-mentioned three parthousings fastened together by bolts, thereby requiring two processes ofpositioning and bolting to fasten them. Thus, it is complicated andexpensive to assemble the housing.

It is conceivable for a single housing member to replace the front andmiddle part housings. In this way, only a process of fastening thesingle housing member and the rear axle housing is required tomanufacture a housing for the transmission. However, the main-clutchsystem and the speed-changing system must be housed in the housingmember, wherein each of the systems requires to be settled easily andsupported steadily.

Referring to the conventional speed-changing lever, the supportingportions for the lever are formed integrally with the transmissioncasing, thereby complicating manufacture of the transmission casing andincreasing its price, especially when a plurality of supporting portionsare formed in correspondence to a plurality of levers.

Referring to the conventional front-wheel driving PTO system, the unittherefor is partly housed in the transmission casing so as to bedisposed at a longitudinally intermediate space of the speed-changingsystem or at a rear space, whereby the distance between the unit and thefront-wheel driving unit disposed between left and right front wheels islong. Thus, the transmission shaft between both of the units must belong, thereby causing a high manufacturing cost and lowering theefficiency of front-wheel driving. Therefore it is desirable for thefront-wheel driving PTO unit to be near the front-wheel driving unit.

The transmission shown in Japanese Patent No. Hei 5-26686 is constructedbetween a travelling-input shaft drivingly connected with an engine of aworking vehicle like a tractor and a travelling-output shaft drivinglyconnected with rear wheels. The two shafts are disposed in parallel toeach other. It is a combination of previous first speed-changingarrangement which can appear three ranges of high-speed advancing,low-speed advancing and reversing and subsequent second speed-changingarrangement which can appear multi-speed stages in every range of firstspeed-changing arrangement. The first and second speed-changingarrangement are disposed in front and rear of a vehicle body, therebycausing the transmission as a whole to be longitudinally long. If aclutch device for creeping-speed range is additionally provided, thelength is increased even further.

If the first and second speed-changing arrangement are disposed inparallel or overlap in a longitudinal direction, the transmission can belongitudinally shortened, thereby compacting the vehicle. Also, thefront-wheel driving PTO unit can be disposed further forward so as toapproach the front-wheel driving unit, thereby improving efficiency offront-wheel driving.

Referring to shift patterns of the speed-changing levers described inJapanese Patent No. Hei 5-26686, a lever for operating the firstspeed-changing arrangement is shifted along a straight slot, and a leverfor operating the second speed-changing arrangement is shifted along anH-like shaped slot. However, the second speed-changing arrangement formulti-speed-changing is used rather frequently when travelling, therebyrequiring it to be operable more simply.

SUMMARY OF THE INVENTION

The transmission for a working vehicle in accordance with the presentinvention is provided with an integral transmission housing forcontaining a main-clutch system and a speed-changing system interposedbetween an engine and a rear axle housing containing a rear-wheeldifferential unit for the purpose of simplifying an assembly of itshousing. The assembly and disassembly of the housing can be completed ina single process of joining and disjoining the transmission housing andthe rear axle housing though bolts.

An object of the present invention is to provide a transmissionincluding the transmission housing, whose main-clutch system andspeed-changing system are disposed in the transmission housing so as tobe compact (particularly, longitudinally short) and convenient tomaintain, and whose means having relations with the speed-changingsystem, e.g., front-wheel driving PTO unit, speed-changing operatingmeans and PTO shaft are disposed so as to be compact, convenient tomaintain and nicely operable.

To achieve this object, the transmission housing is provided at itsfront and rear ends with openings respectively and at its interior witha partition wall so as to be divided before and behind into a frontchamber and a rear chamber respectively. The main-clutch systemcontinuously combined with an output area of an engine is inserted intothe front chamber through the front end opening of the transmissionhousing to be settled therein. The speed-changing system drivinglyfollowing the main-clutch system is inserted into the rear chamberthrough the rear end opening of the transmission housing to be settledtherein. A bearing plate is fixed on either the transmission housing orthe rear axle housing so as to be disposed in vicinity of the rear endopening of the transmission housing and the front end opening of therear axle housing, whereby the speed-changing system is supportedbetween the partition wall and the bearing plate in the rear chamber.

Accordingly, the main-clutch system and the speed-changing system can beremovably settled easily in the transmission housing before and behindthe partition wall by manner of their insertion through the front andrear end openings. Also, the interiors of the transmission housing andthe rear axle housing can be divided by the simple bearing plate. Thebearing plate can be easily disposed by being fastened to eitherhousing. The settled bearing plate can support the rear end of thespeed-changing system in the rear chamber, and can also support thefront ends of the travelling-output system and the rear-PTO-outputsystem in the rear axle housing. Thus, the invention can provide atransmission for a working vehicle whose inner systems and housing canbe assembled and disassembled easily.

Preferably, the bearing plate is provided with a lubricating oilproviding port for leading the oil in the transmission housing tolubricated areas of the speed-changing system.

In this lubricating construction, the lubricated areas of thespeed-changing system can be supplied with sufficient lubricating oil,thereby improving the efficiency and durability of the speed-changingsystem.

The speed-changing system in the rear chamber is a transmissionconstructed between a travelling-input shaft provided thereon with themain-clutch system so as to be longitudinally supported in the frontchamber and a travelling-output shaft disposed in parallel to thetravelling-input shaft so as to be drivingly connected with the rearaxles. It comprises three parallel shafts (i.e., a first speed-changingshaft, a second speed-changing shaft and a travelling-output shaft)provided thereon with a reversing arrangement and a multi-speed-changingarrangement. The first speed-changing shaft, which always drivinglyfollows the travelling-input shaft, is disposed in parallel to thetravelling-output shaft. The second speed-changing shaft in parallel tothe first speed-changing shaft is disposed co-axially with thetravelling-input shaft so as to face the travelling-input shaft.

Since the reversing arrangement and the multi-speed-changing arrangementconstituting the speed-changing system, which have been conventionallyseparately disposed before and behind, overlap longitudinally by theirdisposal on the parallel shafts between the partition wall and thebearing plate, the transmission as a whole can be longitudinally short,so as to be advantageous in making the vehicle more compact and indisposing a below discussed front-wheel driving PTO unit forward so asto approach the front-wheel driving unit.

The travelling-input shaft is disposed at a substantially lateral centerin the transmission housing. The first and second speed-changing shaftsare disposed respectively at both lateral sides of the travelling-inputshaft.

Thus, the three shafts of the transmission can be compactly contained inthe rear chamber so that the gears on the shafts may effectively engagewith one another.

The travelling-output shaft is provided thereon with a front-wheeldriving PTO gear drivingly connected to front wheels and is disposedbelow the first speed-changing shaft, whereby the front-wheel drivingPTO gear approaches a front-wheel driving PTO unit (discussed below) soas to compact the unit.

A front-wheel driving PTO unit is attached to a bottom of thetransmission housing facing the rear chamber. A front-wheel driving PTOgear for transmitting power taken from the speed-changing system to theunit is rotatably supported by the bearing plate in the rear chamber.

Since the front-wheel driving PTO gear is disposed close to thepartition wall as a front wall of the rear chamber, the distance betweenthe front-wheel driving PTO unit and a front-wheel driving unit betweenleft and right front wheels can be short, thereby reducing themanufacturing cost of a universal joint interposed therebetween andimproving the efficiency of the front-wheel driving unit.

The travelling-input shaft and the second speed-changing shaft are madeto be cylindrical. A rear-PTO transmission shaft is disposed to passthrough both of the cylindrical shafts.

Accordingly, the rear-PTO transmission shaft can be disposed togetherwith the travelling transmission in the same space, thereby compactingthe entire transmission.

For the reversing arrangement, a first drive gear and a second drivegear are rotatably provided on the first speed-changing shaft. The firstdrive gear decelerates the second speed-changing shaft in regulardirected rotation. The second drive gear always engages with an idlinggear rotatably provided on the travelling-output shaft for reverselyrotating the second speed-changing shaft. A first clutch device isprovided for selectively connecting the first speed-changing shaft toeither the first or second drive gear. A second clutch device isinterposed between the travelling-input shaft and the secondspeed-changing shaft so as to directly connect both the shafts only whenboth of the first and second drive gears are disconnected.

For the multi-speed-changing arrangement, a plurality of drive gears arefixedly provided on the second speed-changing shaft. A plurality ofdriven gears are relatively rotatably provided on the travelling-outputshaft which respectively engage with the drive gears on the secondspeed-changing shaft. A third clutch device is provided for selectivelyconnecting one of the driven gears with the travelling-output shaft.

Thus, the reversing switching arrangement and the multi-speed-changingarrangement are compactly structured. The gear trains and the clutchdevices of the pair of arrangements overlap longitudinally, therebylongitudinally shortening the transmission. Double power transmittingbetween the first and second speed-changing shafts can be avoidedbecause the second clutch device connects the travelling-input shaft andthe second speed-changing shaft only when the first clutch device isneutral.

With regard to the reversing arrangement, the first drive gear alwaysengages with one of drive gears on the second speed-changing shaft andthe idling gear, which engages with the second drive gear, also alwaysengages with another of the drive gears on the same shaft.

Thus, the drive gears for multi-speed-changing are also used for theadvancing-gear train and the reversing-gear train, thereby reducing thenumber of gears.

At least one of the first, second and third clutch devices is providedwith a synchronizer.

In this construction, the clutch device can be smoothly operable,thereby easing the operation thereof and reducing shock in connectingand disconnecting thereof.

The first and second clutch devices are selectively operable by alongitudinally and laterally rotatable first (sub) speed-changing lever,thereby reducing the number of parts therefor and easingadvancing-and-reversing switching operation.

The third clutch device is operable by a second (main) speed-changinglever longitudinally movable along a straight shift pattern so as toprovide multi-speed stages through the multi-speed-changing arrangement,thereby easing multi-speed-changing operation in comparison with theconventional multi-speed-changing lever which has been complicated inoperation along a shift pattern having various directions.

The first and second speed-changing levers are respectively supported toboth lateral sides of a cover enclosing an opening bored through anouter wall of the housing toward the rear chamber therein.

Accordingly, each of the first and second speed-changing lever, whichhas been conventionally supported by a housing directly, can be easilyconnected and disconnected to the speed-changing system in the rearchamber simply by attaching and detaching the cover integrallysupporting the levers to the transmission housing. When supporting aplurality of levers (which are provided respectively for the abovementioned pair of arrangements of the speed-changing system), theconventional speed-changing lever supporting construction has been morecomplicated, however, the first and second speed-changing leverssupported by the cover in accordance with the invention can be connectedand disconnected to respective arrangements of speed-changing system inthe transmission housing easily. Moreover, the levers can be separatelydisposed easily on both sides of a seat. The transmission housing can besimply formed so as to be manufactured at a low price because it isseparated from the cover supporting the levers.

Clutch fork shafts for the speed-changing system are axially slidablysupported between the partition wall and the bearing plate in the counerspaces of the rear chamber facing the interior of the cover through theopening of the transmission housing, whereby they can be easily andsimply disposed in the transmission housing so as to be connected anddisconnected to respective speed-changing levers easily.

Connecting members for connecting the speed-changing levers and theclutch fork shafts are detachably attached to respective upper surfacesof the clutch fork shafts through the opening enclosed by the cover.Thus, the connecting members of the clutch fork shafts can be assembledand disassembled easily.

Each of the connecting members is provided with a neutral returningmember for biasing an operating shaft of a basic end of thespeed-changing lever toward its neutral position.

Accordingly, the speed-changing lever is naturally fixedly located atthe neutral position when an operator releases his hand from it. Thespeed-changing lever is provided from waste rotation against forceapplied thereon.

Moreover, referring to the transmission additionally provided with acreeping speed range, between the first and second speed-changing shaftsare interposed three gear trains (i.e., a regular speed-reduction geartrain, a reversing gear train and a creeping speed-reduction geartrain). Between the second speed-changing shaft and thetravelling-output shaft are interposed a plurality of speed-reductiongear trains for multi-speed. A first clutch device is provided on thefirst speed-changing shaft. It selectively engages with either theregular speed-reduction gear train or the reversing gear train so as totransmit power between the first and second speed-changing shaftsthrough the selected gear train. A second clutch device is provided onthe second speed-changing shaft. It selectively connects thetravelling-input shaft with the second speed-changing shaft directly orengages with the creeping speed-reduction gear train so as to transmitpower between the first and second speed-changing shafts only when theregular speed-reduction gear and the reversing gear are disconnected. Athird clutch device is provided on the travelling-output shaft so as toselectively connect one of the speed-reduction gear trains between thesecond speed-changing shaft and the travelling-output shaft.

In this construction, the gear trains, to which one for creeping-speedrange is added, are disposed so as to overlap longitudinally and thefirst, second and third clutch devices can be laterally divided, therebycompacting and longitudinally shortening the transmission as a whole.

The first and second clutch devices are selectively operated by a lever,i.e., the first speed-changing lever which is movable to both oppositedirections from the neutral position.

Thus, the first and second clutch devices can be selectively operated bya single speed-changing lever (the first speed-changing lever) so as toappear a reversing range, a low-speed advancing range, a creeping-speedadvancing range and a high-speed advancing range, thereby easingoperation of advancing-and-reversing switching operation and reducingthe number of parts therefor.

The creeping speed-reduction gear train consists of a drive gear fixedon the first speed-changing shaft, a driven gear relatively rotatablyprovided on the second speed-changing shaft and a group of gearsconnecting the drive and driven gears. The group of gears are supportedby a lid which is detachably attached to the transmission housing.

Thus, a creeping speed-reduction gear train constructed in such a mannercan be easily attached to the transmission of a vehicle requiring acreeping-speed range.

Other and further objects, features and advantages of the presentinvention will appear more fully from the following description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a whole side view of a tractor provided with a transmission inaccordance with a first embodiment of the present invention;

FIG. 2 is a schematic sectional side view of housings for thetransmission and a diagram of the transmitting system therein inaccordance with the first embodiment.

FIG. 3 is a sectional side view of a first chamber A in a transmissionhousing 1 showing a main-clutch system therein;

FIG. 4 is a sectional development side view of a second chamber B in atransmission housing 1 showing a speed-changing system therein and afront-wheel driving PTO unit in accordance with the first embodiment;

FIG. 5 is a fragmentary sectional development side view of the sameshowing the speed-changing system in second camber B;

FIG. 6 is a sectional rear view of a rear axle housing 2 showing abearing plate 3 having a lubricating oil providing port for thespeed-changing system in second chamber B;

FIG. 7 is a sectional front view of the tractor showing a seat andspeed-changing levers in accordance with the first embodiment;

FIG. 8 is an exploded perspective view of transmission housing 1 showingthat a cover 51 supporting speed-changing levers is attached to housing1 in accordance with the same embodiment;

FIG. 9 is a sectional plan view of second chamber B in transmissionhousing 1 showing clutch fork shafts disposed therein in accordance withthe first embodiment;

FIG. 10 is a sectional front view of second chamber B in transmissionhousing 1 showing clutch devices disposed therein in accordance with thefirst embodiment;

FIG. 11 is an exploded perspective view of connecting members 61 and 62and clutch shafts 58 and 59;

FIG. 12 is a fragmentary front view of rear axle housing 2 showingbearing plate 3 having detent mechanisms for clutch fork shafts inaccordance with the first embodiment;

FIG. 13 is an exploded perspective view of a detent mechanism in bearingplate 3;

FIG. 14 is a whole side view of a tractor provided with a transmissionin accordance with a second embodiment of the present invention;

FIG. 15 is a schematic sectional side view of housings for thetransmission and a diagram of the transmitting system therein inaccordance with the second embodiment;

FIG. 16 is a fragmentary sectional development side view of secondchamber B in transmission housing 1 showing a speed-changing systemtherein in accordance with the second embodiment;

FIG. 17 is a fragmentary sectional development plan view of secondchamber B in transmission housing 1 showing a creeper gear unit inaccordance with the second embodiment;

FIG. 18 is a sectional front view of second chamber B in transmissionhousing 1 showing clutch devices disposed therein in accordance with thesecond embodiment;

FIG. 19 is an exploded perspective view of transmission housing 1showing that cover 51 supporting speed-changing levers is attached tohousing 1 in accordance with the second embodiment;

FIG. 20 is a sectional front view of the tractor showing a seat andspeed-changing levers in accordance with the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With the above mentioned and other objects in view, the presentinvention consists in the methods and the construction hereinafter fullydescribed, illustrated in the accompanying drawings, and set forth inthe claims hereto appended, it being understood that various changes inthe operation, form, proportion and minor details of construction,within the scope of the claims, may be resorted to without departingfrom the spirit of the present invention or sacrificing any of theadvantages thereof.

At first, explanation will be generally given to a tractor as anembodiment of a working vehicle employing a transmission of the presentinvention. An engine E is disposed on a front frame 83 in front of thetractor. Frame 83 and engine E are covered with a bonnet 84. In bonnet84, a radiator 85 is disposed before engine E and a muffler 86 isdisposed above engine E. An exhaust pipe 87 extends from muffler 86 soas to project outside bonnet 84. A rear end of bonnet 84 is close to adashboard 88 provided with a steering wheel 89. Behind dashboard 88 aredisposed left and right fenders 90 covering left and right rear wheels78. Between fenders 90, a seat 91 is disposed and a main (second)speed-change lever 52 and a sub (first) speed-change lever 55 aredisposed respectively on both sides of seat 91 as shown in FIG. 11.

A transmission housing 1 is fastened at its front end to an outputportion provided on the rear end of engine E by bolts and is extendedrearward so as to pass through below seat 91 and to be fastened at itsrear end to a front end of a rear axle housing 2 disposed between leftand right rear wheels 78 by bolts, thereby forming a combinationtransmission housing and vehicle body frame. Housing 1 consists of afront housing half 1F and a rear housing half 1R fastened to each otherby bolts.

In housing 2 are contained a rear-wheel differential drive system and arear-PTO system. Rear axles 77 are journalled by left and right sideportions of housing 2 and rear wheels 78 are respectively attached toouter ends of rear axles 77. On housing 2 is mounted a hydraulic liftingdevice 92 having lift arms 93 for moving a working machine attached tothe rear of the tractor up and down. A PTO shaft 18 projects rearwardfrom a cover 17 attached to the rear surface of housing 2 fortransmitting power of engine E into the working machine.

Furthermore, a front-axle housing 80 for housing a front-wheeldifferential drive system and journalling left and right front axles 81is disposed under frame 83. Left and right front wheels 82 are attachedto outer ends of front axles 81. A front-wheel driving PTO casing 4 isattached to the bottom of housing 1. A front-wheel driving PTO shaft 20is extended forward from casing 4 and is connected to the frontdifferential drive system in housing 80 through a joint shaft 79. Thus,power is transmitted from a speed-changing system in housing 1 intofront wheels 82 on front axles 81.

Explanation will be now given to a general inner construction of thetransmission in accordance with FIG. 2 or others. An interior oftransmission housing 1 is divided before and behind into a front chamberA and a rear chamber B by a partition wall 1a vertically formed at alongitudinally intermediate portion in rear housing half 1R. As shown inFIG. 3, a housing means defining front chamber A consists of fronthousing half 1F and a front half portion of rear housing half 1R. Afront end of housing half 1F is open and is peripherally provided with aflange 1d so as to be fastened to the rear end of engine E by bolts asshown in FIG. 1. In front chamber A and in front of partition wall 1a isdisposed a bearing wall 1b integrally formed by housing half 1R. Acylindrical travelling-input shaft 7 is substantially longitudinallyhorizontally journalled by partition wall 1a and bearing wall 1b. Shaft7 is extended further forward from wall 1b so that a clutch disk 6 isfixed onto its front end.

In front chamber A of housing 1 is contained a flywheel 5 directlyconnected with a crankshaft of engine E. A main-clutch system of commondry single disk type is constructed between flywheel 5 and disk 6. Asshown in FIG. 3, a cylindrical support shaft 76b is fixed at its rearend onto a front surface of wall 1b of housing 1 so thattravelling-input shaft 7 is relatively rotatably inserted into shaft76b. A release bearing 76a connected to a clutch arm 76 is axiallyslidably provided on shaft 76b and abuts at its front end against alever 5a for switching operation of the main-clutch system. When aclutch pedal provided on the tractor is trod, arm 76 is rotatedcounterclockwise so as to slide bearing 76a forward, thereby pushinglever 5a. Thus, disk 6 is separated from flywheel 5 so that amain-clutch is disengaged. When a foot is released from the clutchpedal, arm 76, bearing 76a and lever 5a return to the position as shownin FIG. 3 by a biasing spring (not shown). Thus, disk 6 is pressedagainst flywheel 5 so that the main-clutch is engaged. Additionally, adamping spring 6a is inserted into disk 6 to prevent direct propagationof vibration from flywheel 5 provided integrally with engine E totravelling-input shaft 7 while rotational transmission from disk 6pressed against flywheel 5 to shaft 7.

A first PTO transmitting shaft 13 passes through shaft 7 and extendsforward from the front end thereof so as to be directly connected toflywheel 5 through a disk 12.

The main-clutch system as a unit together with flywheel 5 can beinserted into front chamber A through the front end opening ofhousing 1. The main clutch inserted in such a manner is supported at itsintermediate portion by bearing wall 1b and at its rear end by partitionwall 1a. It can be settled in front chamber A easily.

With regard to a rear half portion of transmission housing 1, a rearopen end thereof is provided with flange 1e so as to be fastened toflange 2d provided around a front end of rear axle housing 2 by bolts. Aplurality of bosses 2a integrally project inwardly from the innersurface of the front end opening of housing 2. A bearing plate 3 isdisposed as a rear end wall of rear chamber B so as to be fastened tofront surfaces of bosses 2a by bolts as shown in FIG. 6. In this regard,similar bosses may alternatively project from the rear end opening ofhousing 1 for fastening plate 3.

In rear chamber B, three shafts for speed-changing are substantiallylongitudinally horizontally journalled in parallel with one anotherbetween wall 1a and plate 3. The three shafts are a first speed-changingshaft 8, which always rotationally follows travelling-input shaft 7, asecond speed-changing shaft 9, which is disposed co-axially with shaft 7so as to face at its front end to the rear end of shaft 7, and atravelling-output shaft 10, which is continuously connected to apropeller shaft 11 discussed below. Shaft 9 is cylindrically shapedsimilar to shaft 7. A second PTO transmitting shaft 14 passes throughshaft 9 so as to be continuously joined with first PTO transmittingshaft 13 through a joint 95 in a rear boss 7a fixedly extending rearwardfrom the rear end of shaft 7. A rear end of shaft 14 extends rearwardfrom plate 3 so as to be connected to a rear-PTO clutch in housing 2.

The three speed-changing shafts 8, 9 and 10 defining a speed-changingsystem in the transmission are previously supported by plate 3 fixed tothe front end of housing 2 before fastening housings 1 and 2 by bolts.At this time, there is shaft 14 passing through shaft 9. In housing 1,there is shaft 7 supported by wall 1a.

On fastening housings 1 and 2, shafts 8, 9 and 10 extending forward fromplate 3 are inserted into housing 1 through the rear end openingthereof. When flanges 1e and 2d of housings 1 and 2 are fastened to eachother, the front ends of shafts 8 and 10 are inserted respectively intobearings provided in wall 1a and the front ends of shafts 9 and 14 areinserted into rear boss 7a of shaft 7. Thus, each of shafts 8, 9, 10 and14 are naturally settled in rear chamber B simply by positioning flanges1e and 2d in relation to each other.

Referring to FIG. 10, there is shown an arrangement of shafts 8, 9, 10and 14 in rear chamber B when viewed in front. In this regard, shafts 7and 9 are disposed at a substantially lateral center of housing 1,thereby ensuring sufficient space on both lateral sides of shaft 9 inrear chamber B. In this embodiment, shaft 8 is disposed in theright-hand space below shaft 9 and shaft 10 is in the left-hand spacethereof. (Left and right are defined by viewing from the front. The sameshall apply hereinafter.).

In casing 4 attached to the bottom of the portion of housing 1 formingrear chamber B are rotatably supported a support shaft 19 andfront-wheel driving PTO shaft 20, so as to form a transmitting systembetween shafts 10 and 20 through shaft 19 and a gear train. Shaft 10 isdisposed lower than shaft 8 as shown in FIG. 10, so that thetransmitting system between shafts 10 and 20 can be compacted byreducing the distance between shafts 10 and 19.

Housing 2 forms a first bearing wall 2b and a second bearing wall 2cbefore and behind therein. A rear-wheel differential 21 is disposedbetween walls 2b and 2c. Propeller shaft 11 is rotatably supportedbetween plate 3 and wall 2b. As shown in FIG. 4, a front end of shaft 11is joined with a rear end of shaft 10 through a joint 10a provided inplate 3. As shown in FIG. 2, a rear end of shaft 11 projecting inwardlyfrom wall 2b is provided thereon with a bevel pinion 11a so as to engagewith a large bevel gear of differential 21.

As shown in FIG. 2, a PTO brake casing 75 is fixed onto a front surfaceof wall 2b. A PTO clutch casing 73 is disposed in front of casing 75.PTO clutch disks 72 are provided on a rear end of shaft 14 projectingrearward from plate 3. A third PTO transmitting shaft 15 is disposedbehind the rear end of shaft 14 along the same axis. Casing 73 is fixedon shaft 15 and contains a hydraulic piston for pressing and releasingdisks 72 against and from casing 73 so as to define a hydraulic PTOclutch system of multi wet frictional disk type.

PTO brake disks 74 are provided on a boss projecting rearward from arear surface of casing 73. Casing 75 contains a hydraulic piston forpressing and releasing disks 74 against and from casing 75 so as todefine a hydraulic PTO brake system of multi wet frictional disk type.The piston of the PTO brake system acts so as to press disks 74 againstcasing 75 for braking shaft 15 only while the piston of the PTO clutchsystem is set off the PTO clutch. Shaft 15 passes through casing 75, isjournalled by wall 2b and extends further rearward so as to be fixedlyconnected to a front end of a PTO counter shaft 16 journalled by wall2c.

Rear cover 17 is fastened to a rear opening end of housing 2 by bolts,as best seen in FIG. 2. In housing 2, there are PTO counter shaft 16 andPTO shaft 18 rotatably supported substantially longitudinallyhorizontally between wall 2c and cover 17 and connected with each otherthrough a speed-reduction gear train. A front end of shaft 16 projectsforward from wall 2c so as to be joined with shaft 15.

Explanation will be now given to the detailed construction of thespeed-changing system, which is contained in rear chamber B, in theabove mentioned transmission for a working vehicle having a housingconstruction comprising housings 1 and 2 and casing 4 in accordance withFIGS. 2 and between 4 and 13. As shown in FIGS. 4 and 5, aspeed-changing input gear 22 is fixed onto rear boss 7a of shaft 7projecting into rear chamber B from wall 1a. The front end of shaft 9 isrelatively rotatably supported in boss 7a through a needle bearing. Athrust bearing 96 for receiving the thrust force from shaft 9 isdisposed in boss 7a. Thus, shafts 7 and 9 are disposed sequentially onthe same axis.

As shown in FIG. 5, a gear 23 is fixed on a front end portion of shaft 8in parallel with shafts 9 and 14. Gear 23 always engages with gear 22. Afirst drive gear 24 and a second drive gear 25 are relatively rotatablyprovided on a rear half portion of shaft 8. Also, a first clutch deviceC1 with a synchronizer is provided thereon for selectively engagingeither of gears 24 and 25 with shaft 8. First clutch device C1 can beturned into a position to engage gear 24 with shaft 8, a position toengage gear 25 with shaft 8 and a neutral position to engage none ofgears 24 and 25 with shaft 8 by longitudinally slide of a clutch sleeve(a synchronizer sleeve) 42 thereof according to longitudinal motion of aclutch fork 41. As shown in FIG. 9, a clutch fork shaft 58 islongitudinally slidably spanned between wall 1a and plate 3 so as topass through a boss of clutch fork 41. The boss is fixed to clutch forkshaft 58 through a spring pin 97 so as to be axially movable, wherebyclutch fork 41 longitudinally slides integrally with shaft 58.

Referring to FIGS. 5, 6 and 9, there is shown a mechanism for forcelysupply of lubricating oil to the synchronizer. An oil sump 3a is formedin plate 3 which supports the rear end of shaft 8. An oil conduit 71 incommunication with sump 3a is connected to a side surface of plate 3 soas to communicate with an oil hole 2e which is open at an outer sidesurface of housing 2. Into hole 2e is led oil drained from a hydraulicdevice provided on a vehicle (e.g., a power steering device for frontwheels or hydraulic lifting device 92) through a conduit 100. In thisembodiment, the oil drained from a pressure oil supplying and drainingcircuit 99 for a power steering cylinder 98 is used. Additionally, asshown in FIG. 14, for the purpose of supplying circuit 99 with surplusoil in housing 2 as pressure oil for cylinder 98, a strainer 101a isspanned in vicinity of a front bottom portion of housing 2 so as tocross shaft 11. The lubricating oil absorbed into strainer 101a is takenout from housing 2 through an oil suction passage 2f in a side wall ofhousing 2 and a line filter 101b attached onto the side wall and ischarged into circuit 99 by a hydraulic pump M. If the oil drained fromhydraulic lifting device 92 is led into housing 2, a hydraulic cylinderfor lift arms 93 should replace cylinder 99 and a pressure oil chargingand draining circuit in device 92 should replace circuit 99.

As shown in FIG. 5, a lubricating oil passage 8a is bored in shaft 8.Exit of passage 8a is open at the round surface of shaft 8 near splinesprovided thereon for fitting to the synchronizer. Entrance of passage 8ais open at the rear end surface of shaft 8 so as to communicate withsump 3a, thereby forcely supplying a frictionable portion of thesynchronizer with lubricating oil. Sump 3a is a recessed portion of therear surface of plate 3 and is covered with a lid 69. A relief valve 70for limiting the pressure of lubricating oil is attached to lid 69. Whenthe pressure of oil led into sump 3a exceeds the limit thereof, thesurplus oil is drained into housing 2 behind sump 3a. As shown in FIGS.5 and 6, sump 3a is also made to supply lubricating oil into the spacebetween shafts 9 and 14 or its vicinity (e.g., bearing 96 and splines ofshaft 14) which requires lubrication. Thus, sump 3a has distributivefunction of lubricating oil.

Onto the front end of shaft 9 is fixed a first-speed drive gear 26forming a clutch gear 26a at its front end. A rear end of gear 22 isformed into a clutch gear 22a, which is disposed just before gear 26a.Between gears 26a and 22a is disposed a longitudinally slidable clutchsleeve 44 which engages with a clutch fork 43, thereby constructing asecond clutch device C2. As shown in FIG. 9, a clutch fork shaft 59longitudinally slidably spanned between wall 1a and plate 3 passesthrough a boss of clutch fork 43. The boss is fixed onto shaft 59through a spring pin 97, whereby clutch fork 43 slides integrally withshaft 59.

Second clutch device C2 can be changed into a state that sleeve 44engages with only gear 26a so as to separate shafts 7 and 9 from eachother and a state that sleeve 44 engages with both gears 26a and 22a soas to connect shafts 7 and 9 with each other directly. In the formerstate, the rotational power of shaft 7 is transmitted to shaft 8 throughthe speed reduction gear train of gears 22 and 23 and is transmitted toshaft 9 through either gear 24 or 25 clutched on by sleeve 42. In thelatter state, the rotational power of shaft 7 is directly transmittedinto shaft 9. At this time, shaft 10 rotationally follows shaft 9 in thedirection for advancing of a vehicle.

Second clutch device C2 is so restricted that clutch fork 43 can slideforward so as to move sleeve 44 to the position where it engages withboth gears 26a and 22a (i.e., a clutching on position thereof) only whenfirst clutch device C1 is neutral. Thus, when second clutch device C2 isengaged, shaft 8 runs idle and does not drive shaft 9, whereby shaft 9directly driven by shaft 7 can be prevented from receiving doubledriving powers.

On the contrary, first clutch device C1 is so restricted that eithergear 24 or 25 can engage with shaft 8 only when sleeve 44 is set at theposition where it engages with only gear 26a (i.e., a neutral positionof second clutch device C2). Thus, the route of power transmittingbetween shafts 7 and 9 through shaft 8 can be ensured.

The restrictive mechanism of sleeves 42 and 44 having the abovementioned functions will be detailed in following description about therelation of the speed-changing system in rear chamber B to levers 55 and52.

Onto shaft 9 are fixed first-speed drive gear 26 having gear 26a, athird-speed drive gear 27, a second-speed drive gear 28 and afourth-speed drive gear 29 in order from front to rear. On shaft 10 arerotatably provided a first-speed driven gear 31, a third-speed drivengear 32, a second-speed driven gear 33 and the fourth-speed driven gear34 in order from front to rear, and are fixed a pair of splined hubs 35and 36 so as to be disposed respectively between gears 31 and 32 andbetween gears 33 and 34. Gears 31, 32, 33 and 34 always engagerespectively with gears 26, 27, 28 and 29 on shaft 9.

Gear 29 also always engages with gear 24 on shaft 8, whereby both gears24 and 29 constitute a regularly rotational speed-reduction gear train.When gear 24 engages with shaft 8 by first clutch device C1, power fromgear 24 is transmitted into shaft 9 through gear 29. The rotary speed ofshaft 10 which rotationally follows shaft 9 in the direction foradvancing of a vehicle is slower than that when second clutch device C2is engaged.

An idling gear 37 is provided on a boss of gear 32 so as to be close togear 32. Gear 25 on shaft 8, gears 37 and 32 on shaft 10 and gear 27 onshaft 9 constitute a reversing gear train. When gear 25 engages withshaft 8 by first clutch device C1, power from gear 25 is transmittedinto shaft 9 through gears 37, 32 and 27. At this time, shaft 9 rotatesshaft 10 in the direction for reversing of the vehicle.

On ends of bosses of gears 31 and 32 facing hub 35 are respectivelyprovided clutch gears 31a and 32a. A front clutch sleeve 47 is disposedaround hub 35 so as to engage with hub 35. Sleeve 47 is rotatable withhub 35 and is axially slidable, so that it can engage with either gear31a or 32a. A front clutch fork 45 is anchored into a peripheral channelof sleeve 47.

Similarly, on ends of bosses of gears 33 and 34 facing hub 36 arerespectively provided clutch gears 33a and 34a. A rear clutch sleeve 48is disposed around hub 36 so as to engage with hub 36. Sleeve 48 isrotatable with hub 36 and is axially slidable, so that it can engagewith either gear 33a or 34a. A rear clutch fork 46 is anchored into aperipheral channel of sleeve 48.

As shown in FIG. 9, a clutch fork shaft 60 passes through bosses ofclutch forks 45 and 46. Clutch fork 45 is fixed to shaft 60 throughspring pin 97. Clutch fork 46 is rotatable around shaft 60 and is notaxially slidable because of another spring pin 97 inserted into shaft 60as a stopper. Thus, on assembling the speed-changing system, clutchforks 45 and 46 can be anchored respectively to sleeves 47 and 48easily, thereby constructing the third clutch device C3 easily.

Clutch forks 45 and 46 and clutch fork shaft 60 are axially movedtogether by a rectilinear operation of second speed-change lever 52,whereby sleeves 47 and 48 integrally slide back and forth. On shaft 10is provided a third clutch device C3 comprising front clutch sleeve 47and clutch gears 31a and 32a on both sides of sleeve 47, and rear clutchsleeve 48 and clutch gears 33a and 34a on both sides of sleeve 48. Thirdclutch device C3 is shifted among four positions as a first-speedposition, a second-speed position, a third-speed position and afourth-speed position by simultaneous sliding of both sleeves 47.

At the first-speed position, clutch gear 31a of first-speed driven gear31 is connected with splined hub 35 through sleeve 47. Clutch sleeve 48engages with only clutch gear 33a of second-speed driven gear 33. Thus,first-speed driven gear 31 engages with shaft 10, so that rotationalpower of shaft 9 is transmitted to shaft 10 through a first speed geartrain of gears 26 and 31.

At the second-speed position (shown in FIG. 5), sleeve 47 engages withonly hub 35 and sleeve 48 connects gear 33a to hub 36, wherebysecond-speed driven gear 33 engages with shaft 10, so that rotationalpower of shaft 9 is transmitted to shaft 10 through a second-speed geartrain of gears 28 and 33.

At the third-speed position, sleeve 48 engages with only hub 36 andsleeve 47 engages with both clutch gear 32a of third-speed driven gear32 and hub 35, whereby gear 32 engages with shaft 10, so that rotationalpower of shaft 9 is transmitted to shaft 10 through a third-speed geartrain of gears 27 and 32.

At the fourth speed position, sleeve 47 engages with only gear 32a andsleeve 48 engages with both hub 36 and clutch gear 34a of fourth-speeddriven gear 34, whereby gear 34 engages with shaft 10, so thatrotational power of shaft 9 is transmitted to shaft 10 through afourth-speed gear train of gears 29 and 34.

Next, explanation will be given to the transmitting system from thespeed-changing system in rear chamber B to front-wheel driving PTO shaft20 in accordance with FIG. 4.

A front-wheel drive gear 30 is fixed onto a portion of shaft 10 close towall 1a as a front end wall of rear chamber B. Support shaft 19 spannedin casing 4 is inserted into rear chamber B through the bottom openingof housing 1, so that a gear 38 rotatably provided on shaft 19 alwaysengages with gear 30. Gear 38 also always engages with a front-wheeldrive input gear 39 fixed on shaft 20 journalled in casing 4. Moreover,a splined hub 40 is fixed onto shaft 20. A front-wheel drive switchingsleeve 50 is axially slidably provided on shaft 20 between hub 40 and aclutch gear 39a formed by gear 39. Clutch sleeve 50 is shifted between aposition where it engages with only hub 40, and a position where itconnects hub 40 and gear 39a with each other, by operation of lever orthe like. When sleeve 50 is at the former position, front wheels 82 arenot driven, whereby a vehicle (a tractor) travels by drive of only rearwheels 78. When at the latter position, power is transmitted from thespeed-changing system in rear chamber B to front wheels 82 whereby thevehicle travels at four wheel drive.

Next, explanation will be given on an attaching construction of main(second) speed change lever 52 and sub (first) speed-change lever 55 asoperating tools for the speed-changing system in rear chamber B and onlinkages interposed between levers 52 and 55 and the speed-changingsystem in gear chamber B. An arrow F shown in FIG. 8 points to the frontof the vehicle.

As shown in FIG. 7, levers 52 and 55 are disposed respectively at bothsides of an operator's seat 91. Guide plates 94L and 94R are disposedrespectively between left fender 20 and seat 91 and between right fender20 and seat 91. Lever 52 passes through a guide slot G1 in plate 94L,and is supported by a left side portion of a cover 51 mounted on anupper surface of a portion of housing 1 forming rear chamber B therein.Lever 55 passes through a guide slot G2 provided in plate 94R and issupported by a right side portion of cover 51. As shown in FIG. 8, cover51 is attached to housing 1 so as to cover an opening 1c at the uppersurface thereof.

As shown in FIG. 8, lever 52 is fixed at its basic end portion onto anouter end of a rotative shaft 52a journalled in the left side wall ofcover 51, so that lever 52 can be rectilinearly shifted among a firstspeed position I, a second speed position II, a third speed position IIIand a fourth speed position IV, which are positioned along I-like shapedguide slot G1. A ball shaped supporter 55a is fixed onto a basic endposition of lever 55 inserted into the right side wall of cover 51 andis retained in the right corner portion of cover 51, so that lever 55can be shifted among a low-speed advancing position L, a reversingposition R, a neutral position N and a high-speed advancing position H,which are positioned along h-like shaped guide slot G2. In cover 51, aconnecting arm (an operating shaft) 52b is fixed onto an inner end ofshaft 52a and an engaging pin (an operating shaft) 55b is extendeddownward slantingly from supporter 55a.

As shown in FIGS. 8 to 10, in an upper right corner space of gearchamber B in housing 1 just below opening 1c are longitudinally axiallyjuxtaposed clutch fork shafts 58 and 59 and in an upper left cornerspace thereof is longitudinally axially disposed clutch fork shaft 60.Each of shafts 58, 59 and 60 is longitudinally slidably journalledbetween wall 1a and plate 3 and can be located by each of detentmechanisms provided within plate 3. The boss of clutch fork 45 piercedby shaft 60 forms a connecting portion 45a on its side surface, wherebyan utmost end of arm 52b is inserted into portion 45a. Instead ofportion 45a, a similar connecting portion may be provided on a sidesurface of the boss of clutch fork 46.

Bosses of clutch forks 41 and 43 are fixed respectively on shafts 58 and59. As shown in FIG. 11, upper surfaces of shafts 58 and 59 disposeddirectly below opening 1c are partly cut horizontally, so as to formsettling surfaces 58a and 59a respectively. Connecting members 61 and 62for engaging with pin 55b are provided on their bottom surfaces withrecessed channels. The bottom channels of members 61 and 62 is settledrespectively on surfaces 58a and 59, so that members 61 and 62 arefastened respectively to shafts 58 and 59 by bolts.

When cover 51 is removed from housing 1, arm 52b and pin 55b arenaturally removed respectively from portion 45a and either member 61 or62, so that levers 52 and 55 can be separated from the speed changingsystem in housing 1 quickly. After housings 1 and 2 are joined with eachother and shafts 58 and 59 are disposed in rear chamber B, members 61and 62 can be inserted into housing 1 through opening 1c so as to beattached to shafts 58 and 59.

In a state that cover 51 provided with levers 52 and 55 is settled ontop of housing 1 and levers 52 and 55 are connected to thespeed-changing system, when lever 52 is shifted along slot G1, the pairof clutch forks 45 and 46 integral with shaft 60 longitudinally slideaccording to shifting of lever 52 through arm 52b and portion 45a, sothat the pair of sleeves 47 and 48 are shifted among the above mentionedfour speed positions.

Pin 55b is made to engage with either member 61 or 62 by lateral motionof lever 55. In case of pin 55b engaging with member 61, when lever 55is longitudinally shifted, sleeve 42 is shifted among three positions ofreversing position R, neutral position N and low-speed advancingposition L through shaft 58 and clutch fork 41. In case of pin 55bengaging with member 62, when lever 55 is longitudinally shifted, sleeve44 is shifted between two positions of high-speed advancing position Hand neutral position N through shaft 59 and clutch fork 43.

Members 61 and 62 are provided on their tops with successivelly slantingportions. At an upper end of the slanting portion of member 61 and at alower end of the slanting portion of member 62 are provided recessedportions. Both the recessed portions face each other so as to bearranged on a lateral slanting line when both shafts 58 and 59 are attheir neutral positions. In this state, pin 55b can move between therecessed positions of members 61 and 62 by lateral motion of lever 55along slot G2. As shown in FIGS. 10 and 11, member 61 is provided with abiasing member 63 for biasing pin 55b toward member 62 and member 62 isprovided with a biasing member 64 for biasing pin 55b toward member 61.Biasing members 63 and 64 are disposed respectively in through-holes 61aand 62a which penetrate respectively in members 61 and 62 so as tocommunicate with the recessed portions thereof. Member 63 comprises pin63a for abutting against the utmost end of pin 55b, plug 63b forplugging an outside opening of through-hole 61a and a spring 63cinterposed between pin 63a and plug 63b for pushing pin 63a toward Pin55b. Member 64 similarly comprises a pin 64a, a plug 64b and a spring64c. When both shafts 58 and 59 are positioned at their neutralposition, pin 55b receives both biasing forces of pins 63a and 64a, soas to be positioned at the middle between members 61 and 62, wherebylever 55 is positioned at neutral position N of slot G2. For anchoringpin 55b to either member 61 or 62, lever 55 is vertically swung oncentering supporter 55a against biasing forces of springs 63c and 64c.

Referring to FIGS. 9, 12 and 13, there are shown the detent mechanismsfor locating shafts 58, 59 and 60. The detent mechanisms are disposed inplate 3. As shown in FIG. 12, three holes 3b are bored in plate 3 forjournalling shafts 58, 59 and 60 respectively therein. Plate 3 isprovided on the front surface thereof with three channels 3c which isrectangular when viewed in front and is sectionally U-like shaped (asshown lit FIG. 13). Channels 3c communicate with holes 3b respectively.A biasing spring 65 and a detent ball 66 are inserted into each channel3c so that an utmost end of ball 66 faces each hole 3b. After insertionof springs 65 and balls 66, covers 67 and 68 are fastened to the frontsurface of plate 3 so as to cover openings of channels 3c respectively.As shown in FIG. 13, each joint portion 3d between each channel 3c andeach hole 3b is so narrow that only the utmost end of ball 66 projectsinto hole 3b through portion 3d, thereby preventing ball 66 fromentering hole 3b when each of shafts 58, 59 and 60 is removed from hole3b.

As shown in FIG. 9, shaft 58 is provided with three detent channels of areversing index channel 58b, a neutral index channel 58c and alow-speed-advancing index channel 58d in order from behind to before.Shaft 59 is provided with two detent channels of a high-speed-advancingindex channel 59b and a neutral index channel 59c in the same order.Shaft 60 is provided with four detent channels of a first-speed indexchannel 60a, a second-speed index channel 60b, a third-speed indexchannel 60c, and a fourth-speed index channel 60d in the same order.Each ball 66 selectively enters one of detent channels of each shaft 58,59 or 60 by sliding location of shaft 58, 59 or 60 in each hole 3b.

With regard to the speed-changing system of the transmission for aworking vehicle in accordance with this embodiment as shown in FIGS. 1to 13, lever 55 can be shifted among four positions L, H, R and N, andin each of speed ranges defined by three positions L, H and R of lever55, four speed stages can be selected by shift of lever 52 among fourspeed positions I, II, III and IV, whereby the transmission of thisembodiment can provide eight advancing speed stages and four reversingspeed stages in total.

Next, explanation will be given on a modification of the above mentionedtransmission in accordance with FIGS. 14 to 20. Like reference numbersindicate identical or functionally similar elements as those of thefirst embodiment shown in FIGS. 1 to 13 although their figures orconstructions are changed.

With regard to an exterior of the transmission of this embodiment, inFIG. 14, housings 1 and 2 are longitudinally joined with each other andcasing 4 and cover 51 are attached to housing 1 similarly to the firstembodiment. For a different point, a portion of housing 1 forming rearchamber B therein is provided at a side wall thereof with an opening 1dshown in FIG. 17 which is removably covered with a lid 103 shown in FIG.14.

General explanation will be given on the inner construction of thetransmission of this embodiment in accordance with FIG. 15 and others.

Similarly to the first embodiment, the interior of housing 1 is dividedbefore and behind by wall 1a into front chamber A and rear chamber B.Plate 3 is disposed between the rear end of the interior of housing 1and the front end of the interior of housing 2, thereby dividing theinterior of housing into rear chamber B and the interior of housing 2.The respective transmitting constructions including transmitting shafts,gears and the like in front chamber A and housing 2 are similar withthose of the first embodiment.

A transmitting construction in rear chamber B is peculiar to thisembodiment. In this regard, a first creeper shaft 104 and a secondcreeper shaft 105 constituting a creeper transmitting mechanism arejournalled between a pair of bearing walls 103a and 103b projecting froman inner surface of lid 103 into rear chamber B so as to be disposed inrear chamber B in addition to shafts 8, 9, 10 and 14 disposed in rearchamber B and shafts 19 and 20 in casing 4 communicating with rearchamber B. For creeping or superlatively decelerating shafts 10 and 11,a creeper transmitting gear train from shaft 8 to shaft 9 through shafts104 and 105 is constructed as the discussed below.

Referring to FIGS. 15 to 20, there is a detailed description of thespeed-changing system of the transmission of this embodiment. As shownin FIG. 17, similar to the first embodiment, shaft 8 is disposed inparallel to shafts 9 and 14 disposed behind shafts 7 and 13 on the sameaxis and is fixedly provided on its front end portion with gear 23 whichalways engages with gear 22 fixed on the rear end of shaft 7. Shaft 8forms a creeper drive gear 8b on its portion which is a little waybehind gear 23. Gears 25 and 24 are rotatably provided before and behindon the rear half portion of shaft 8. A first double acting clutch deviceC1' is so constructed that a synchronizer is provided between gears 25and 24.

Explanation will be now given on first clutch device C1'. On shaft 8 isfixed a splined hub 42d between both gears 24 and 25. A clutch gear 21aprovided with a synchronizer ring 42b is fitted on gear 24. A clutchgear 25a provided with a synchronizer ring 42c is fitted on gear 25.Clutch sleeve 42 provided with a key 42a is longitudinally slidablyprovided on hub 42d. Clutch fork 41 is anchored into sleeve 42.

While clutch sleeve 42 longitudinally slides from the neutral positionshown in FIG. 16 according to the longitudinal motion of clutch fork 41,first, key 42a pushes either ring 42b or 42c so as to press it againsteither gear 24a or 25a, second, ring 42b or 42c is rotationallysynchronized with gear 24a or 25a, whereby key 42a is released fromsleeve 42 so that sleeve 42 engages with ring 42b or 42c, and finally,with gear 24a or 25a. Thus, one of gears 24 and 25 is selected to fitshaft 8 by first clutch device C1'.

Gears 24 and 25 are rotatably provided on shaft 8 through a bush 24b andbearing 25b, thereby requiring a supply of lubricating oil. Thus, asshown in FIG. 5 similar oil sump 3a is formed in plate 3 as the firstembodiment, into which oil drained from circuit 99 or another oilcircuit is led through conduit 71. A lubricating oil passage 8a' boredin shaft 8 communicates with sump 3a, thereby supplying bush 24b andbearing 25b with enough lubricating oil. Bearing 25b is disposed beforethe recess end portion of passage 8a of the first embodiment. Thus,passage 8a' is extended deeper than passage 8a of the first embodimentand its openings are disposed on the outer surface of shaft 8 close tobearing 25b so as to supply bearing 25b interposed between shaft 8 andgear 25 with enough lubricating oil.

Similar to the first embodiment, lid 69 with relief valve 70 covers sump3a, thereby generating pressure of lubricating oil in sump 3a.Additionally, lubricating oil from sump 3a is divided into a bearing 109supporting the rear end of shaft 9 disposed within plate 3 and intothrust bearing 96 supporting the front end of shaft 9 through the gapbetween shafts 9 and 14.

As shown in FIGS. 16 and 17, on shaft 9 is disposed clutch gear 22a,which is provided with a synchronizer ring 44b and is fixed onto therear end of boss 7a behind gear 22. Behind gear 22a is disposedsecond-speed gear 28 fixed onto shaft 9. A creeper driven gear 108 isrotatably provided on a boss of gear 28. A clutch gear 108a is formed ona front end of boss of gear 108. A splined hub 44c is fixed onto shaft 9between the rear end of boss 7a and the front end of the boss of gear108. Clutch sleeve 44 provided with a key 44c is longitudinally slidablyfitted on hub 44c between clutch gears 22a and 108a. Clutch fork 43 isanchored into sleeve 44. Thus, a second clutch device C2' is provided onshaft 9, whereby selectively gear 22 is fixed to shaft 9 through thesynchronizer or gear 108 is directly fixed thereto.

Second clutch device C2' appears three shift positions of clutch sleeve44. In a neutral position, sleeve 44 engages with none of gears 22a and108a. In a high-speed advancing position, it engages with gear 22a so asto connect shaft 9 to shaft 7 directly. And in a creeping-speedadvancing position, it engages with gear 108a so as to creep shafts 8and 9 through below discussed creeper gear train. The conditions of highspeed advancing and creeping-speed can be selected by second clutchdevice C2' when first clutch device C1' is neutral. The conditions ofreversing and low-speed advancing can be selected by first clutch deviceC1' when second clutch device C2' is neutral.

As shown in FIG. 16, on shaft 9 behind second-speed drive gear 28 arefixedly provided first-speed drive gear 26, third-speed drive gear 27and fourth speed drive gear 29 from before to behind. Second-speeddriven gear 33, first speed driven gear 31, third-speed driven gear 32and fourth speed driven gear 34 rotatably provided on shaft 10 alwaysengage with gears 28, 26, 27 and 29, respectively. Thus, fourspeed-reduction gear trains are disposed between shafts 9 and 10,thereby defining a speed-changing system having four speed stages.

Gear 29 engaging with gear 34 also always engage with gear 24 on shaft8, whereby gears 24 and 29 constitute a speed-reduction gear train forlow-speed advancing. When sleeve 41 of first clutch device C1' engageswith gear 24a (second clutch device C2' is neutral at this time), shaft9 is regularly rotated at reduced speed (in a rotational direction foradvancing).

As shown in FIG. 16, idling gear 37 is fixedly provided on a boss ofgear 32 on shaft 10 and always engages with gear 25 on shaft 8. Whensleeve 41 first clutch device C1' engages with gear 25a (second clutchdevice C2' is neutral), rotational power of shaft 8 is transmitted toshaft 9 through a reversing gear train of gears 25, 37 and 32, wherebyshaft 9 is reversely rotated (in a rotational direction for reversing).

Explanation will be now given on the creeper gear train interposedbetween shafts 8 and 9 in accordance with FIGS. 17 and 18. A firstcreeper 106 is fixed onto first creeper shaft 104 and always engageswith creeper drive gear 8b on shaft 8. A second creeper gear 104a isintegrally formed by shaft 104 and always engages with a third creeper107 fixed onto second creeper shaft 105. A fourth creeper gear 105a isintegrally formed by shaft 105 and always engages with creeper drivengear 108 rotatably provided on shaft 9. When the sleeve of second clutchC2' engages with clutch gear 108a (first clutch device C1' is neutral atthis time), the rotational power of shaft 8 is transmitted to shaft 9through creeper gears 8b, 106, 104, 107, 105a and 108, whereby shaft 9is regularly rotated at creeping speed (in a rotational direction foradvancing).

On shaft 10 is provided a third clutch device C3' for selecting one ofthe four speed-reduction gear trains to be fixedly connected to shaft10. Explanation will be now given on third clutch device C3' inaccordance FIG. 16. Onto shaft 10 is fixed a splined hub 47d betweengears and 31 and is fixed a splined hub 48d between gears 32 and 34.Front clutch sleeve 47 and rear clutch sleeve 48 are axially slidablydisposed on hubs 47a and 48a respectively. Front clutch fork 45 and rearclutch fork 46 are anchored respectively into clutch sleeves 47 and 48.Clutch gears 33a, 31a, 32a and 34a are respectively fixed onto bosses of33, 31, 32 and 34. Sleeve 47 can selectively engage with one of gears33a and 31a through a synchronizer and sleeve 48 can selectively engagewith one of gears 32a and 34a through a synchronizer.

Such third clutch device C3' selects one of gears 33, 31, 32 and 34 tobe connected to shaft 10, whereby driving power is transmitted fromshaft 10 and 11 through the selected speed-reduction gear train.

The transmitting system from the speed changing-system in rear chamber Bto the front-wheel driving PTO system is similar to that of the firstembodiment shown in FIG. 4 and others. In this regard, gear 30 is fixedonto the front portion of shaft 10 in rear chamber B. The rotationalpower of shaft 10 is transmitted to shaft 20 projecting casing 4attached to the bottom of housing 1 through the front-wheel drive geartrain. The vehicle can selectively travel at either four wheel drive ortwo wheel drive by operation of the clutch device provided on shaft 20in casing 4.

Next, explanation will be given on an attaching construction of main(second) speed-change lever 52 and sub (first) speed-change lever 55 asoperating tools for the speed-changing system in rear chamber B and onlinkages interposed between levers 52 and 55 and the speed-changingsystem chamber B in accordance with the second embodiment shown in FIGS.18, 19 and 20.

As shown in FIG. 20, levers 52 and 55 are respectively disposed at leftand right sides of operator's seat 91. Cover 51 is mounted on the top ofhousing 1 forming rear chamber B therein. Both basic ends of levers 52and 55 are respectively supported in retaining portions 51a and 51bformed by cover 51 at left and right corner portions thereof. As alsoshown in FIG. 19, cover 51 is fastened to the top wall of housing 1 bybolts so as to cover opening 1c which is open at the upper surfacethereof. On maintenance of the speed changing system, the bolts arereleased and cover 51 is removed from housing 1, whereby levers 52 and55 can be separated from the speed-changing system in housing 1 easily.

As shown in FIG. 19, lever 52 can be shifted among a neutral position, afirst speed position I, a second-speed position II, a third-speedposition III and a fourth-speed position IV along an H-like shaped guideslot G1' in guide plate 94L inside left fender 90. A ball 52a' formed bythe basic end of lever 52 is rotatably supported by left retainingportion 51a, thereby making lever 52 longitudinally and laterallyrotatable. In cover 51, an engaging pin 52b' projects slantinglydownward.

Lever 55 can be also shifted among a neutral position, a low-speedadvancing position L, a reversing position R, a creeping-speed advancingposition C and a high-speed advancing position H along an H-like shapedguide slot G2' in guide plate 94R inside right fender 90. Similarly tothe first embodiment, ball 55 formed by the basic end of lever 55 isrotatably supported by right retaining portion 51a, thereby making lever55 longitudinally and laterally rotatable. In cover 51, engaging pin 55bprojects slantingly downward.

As show in FIGS. 18 and 19, clutch fork shafts 58 and 59 aresubstantially longitudinally horizontally axially juxtaposed in alateral row in the upper right corner space of rear chamber B just belowopening 1c. A pair of clutch fork shafts 53 and 54 are substantiallylongitudinally horizontally axially juxtaposed in a lateral row in theupper left corner space thereof. Each of clutch shafts 58, 59, 53 and 54is longitudinally slidably journalled between wall 1a and plate 3 andcan be located among longitudinal three positions by each detentmechanism.

Similar to the first embodiment, onto shafts 58 and 59 are respectivelyfixed bosses of clutch forks 41 and 43 and thereon are fixed engagingmembers 61 and 62 for engaging with pin 55b. Onto shafts 53 and 51 arerespectively fixed bosses of clutch forks 45 and 46 and thereon arefixed engaging members 56 and 57 for engaging with pin 52b'.

When cover 51 is removed by the above mentioned manner, pins 52b and 55bare naturally released respectively from members 56, 57, 61 and 62,whereby levers 52 and 55 can be separated from the speed changing systemin rear chamber B. On the contrary, pins 55b and 52b' can naturallyengage with members 61 and 62 and with members 56 and 57 only bysettling cover 51 on housing 1, thereby enabling levers 52 and 55 tointerlock the speed-changing system.

In state that cover 51 supporting levers 52 and 55 is settled on top ofhousing 1 and levers 52 and 55 are connected to the speed-changingsystem, each of clutch fork shafts 53, 54, 58 and 59 can be located byeach detent mechanism among three positions disposed longitudinally.

When lever 55 is neutral so as to dispose both shafts 58 and 59 as shownin FIG. 8, both first and second clutch devices C1' and C2' are neutralas shown in FIG. 16. Then, lever 55 can engage with either member 61 or62 through pin 55b by laterally rotational operation of lever 55 along alateral range of slot G2'.

When lever 55 engaging with member 61 through pin 55b is longitudinallyrotationally operated along a left (i.e., inside) longitudinal range ofslot G2', shaft 58 slides longitudinally, thereby switching first,clutch device C1'. When such lever 55 reaches position L at the frontend of the range of slot G2', first clutch device C1' connects gear 24with shaft 8 for regularly rotating shaft 10 at a low speed. When lever55 reaches position R at the rear end thereof, first clutch device C1'connects gear 25 with shaft 8 for reversely rotating shaft 10.

When lever 55 engaging with member 62 through pin 55b is longitudinally,rotationally operated along a right (i.e., outside) longitudinal rangeof slot G2', shaft 59 slides longitudinally, thereby switching secondclutch device C2'. When such lever 55 reaches position C at the frontend of the range of slot G2', second clutch device C2' connects gear108, with shaft 9 for regularly rotating shaft 10 at a creeping speed.When lever 55 reaches position H at the rear end thereof, second clutchdevice C2' connects shaft 9 with shaft 7 directly for regularly rotatingshaft 10 at a high speed.

When lever is neutral so as to position shafts 53 and 54 as shown inFIG. 19 sleeves 47 and 48 of third clutch device C3' are neutral asshown in FIG. 4. Then, lever 52 can engage with either member 56 or 57through pin 52b' by laterally rotational operation of lever 52 along alateral range of slot G1'.

When lever 52 engaging with member 56 through pin 52b' is longitudinallyrotationally operated along a right (i.e., inside) longitudinal range ofslot G1', shaft 54 slides longitudinally, thereby shifting sleeve 48 ofthird clutch device C3'. When such lever 52 reaches the third speedposition III at the front end of the range of slot G1', sleeve 48connects gear 32 with shaft 10 for rotating shaft 10 at a third speed.When lever 52 reaches the second speed position IV at the rear endthereof, sleeve 48 connects gear 34 with shaft 10 for rotating it at afourth speed.

When lever 52 engaging with member 57 through pin 52b' is longitudinallyrotationally operated along a left (i.e., outside) longitudinal range ofslot G1', shaft 53 slides longitudinally, thereby shifting sleeve 47 ofthird clutch device C3. When such lever 52 reaches the first speedposition I at the front end of the range of slot G1', sleeve 47 connectsgear 31 with shaft 10 at a first speed. When lever 55 reaches the secondspeed position II at the rear end thereof, sleeve 47 connects gear 33with shaft 10 for rotating it at a second speed.

When lever 52 engaging with member 62 through pin 55b is longitudinallyrotationally operated along a right (i.e., outside) longitudinal rangeof slot 62', shaft 59 slides longitudinally, thereby switching secondclutch device C2'. When such lever 55 reaches position C at the frontend of the range of slot G2', second clutch device C2' connects gear 108with shaft 9 for regularly rotating shaft 10 at a creeping speed. Whenlever 55 reaches position H at the rear end thereof, second clutchdevice C2' connects shaft 9 with shaft 7 directly for regularly rotatingshaft 10 at a high speed.

What is claimed is:
 1. A transmission for a working vehicle comprising:arear-axle housing having a travelling output system disposed therein; atransmission housing coupled to said rear-axle housing and interposedbetween an engine and said rear-axle housing, wherein said transmissionhousing has a front end opening and a rear end opening and an interiorof said transmission housing is divided into a first chamber and asecond chamber through a partition wall; a main-clutch system connectedwith an output portion of said engine, wherein said main-clutch systemis inserted into said transmission housing through said front endopening so as to be disposed in said first chamber; a speed-changingsystem for transmitting power from said main-clutch system to drivewheels, wherein said speed-changing system is inserted into saidtransmission housing through said rear end opening so as to be disposedin said second chamber; and a bearing plate attached to said rear-axlehousing and not attached to said transmission housing, said bearingplate forming a rear wall of said transmission housing, wherein saidspeed-changing system is supported between said partition wall and saidbearing plate in said second chamber and a front end of said travellingoutput system is supported by said bearing plate.
 2. A transmission fora working vehicle as set forth in claim 1, wherein said bearing plate isprovided with a lubricating oil providing port for leading oil in saidtransmission housing to a lubricated portion of said speed-changingsystem.
 3. A transmission for a working vehicle as set forth in claim 1,further comprising:a front-wheel driving PTO unit attached to saidtransmission housing, and a gear, through which power taken from saidspeed-changing system is transmitted to said front-wheel driving PTOunit, wherein said gear is disposed adjacent said partition wall in saidsecond chamber.
 4. A transmission for a working vehicle as set forth inclaim 1, wherein said speed-changing system is mechanically combined sothat a reversing arrangement and a multi-speed-changing arrangement areprovided on a plurality of shafts supported in parallel to one anotherbetween said partition wall and said bearing plate.
 5. A transmissionfor a working vehicle as set forth in claim 4, further comprising:anopening provided in an outer wall of said transmission housing so as tocommunicate with said second chamber; a cover provided so as to coversaid opening, and a speed-changing lever supported by said cover forshifting said speed-changing system.
 6. A transmission for a workingvehicle as set forth in claim 5, further comprising:a clutch forksupported by said partition wall and said bearing plate so as to belongitudinally slidable according to shifting operation of saidspeed-changing lever.
 7. A transmission for a working vehicle as setforth in claim 4, further comprising:an opening provided in a top wallof said transmission housing so as to communicate with said secondchamber; a cover provided so as to cover said opening; a firstspeed-changing lever for switching said reversing arrangement, and asecond speed-changing lever for switching said multi-speed-changingarrangement, wherein said first and second speed-changing levers aresupported by said cover.
 8. A transmission for a working vehicle as setforth in claim 7, further comprising:a clutch fork supported by saidpartition wall and said bearing plate so as to be longitudinallyslidable respectively according to shifting operation of said first andsecond speed-changing levers.
 9. A transmission for a working vehiclecomprising:a rear-axle housing having a travelling output systemdisposed therein; a transmission housing coupled to said rear-axlehousing and interposed between an engine and said rear-axle housing,wherein said transmission housing has a front end opening and a rear endopening and an interior of said transmission housing is divided into afirst chamber and a second chamber through a partition wall; amain-clutch system connected with an output portion of said engine,wherein said main-clutch system is inserted into said transmissionhousing through said front end opening so as to be disposed in saidfirst chamber; a speed-changing system for transmitting power from saidmain-clutch system to drive wheels, wherein said speed-changing systemis inserted into said transmission housing through said rear end openingso as to be disposed in said second chamber; and a bearing plateattached to said transmission housing and not attached to said rear-axlehousing, said bearing plate forming a rear wall of said transmissionhousing, wherein said speed-changing system is supported between saidpartition wall and said bearing plate in said second chamber and a frontend of said travelling output system is supported by said bearing plate.10. A transmission for a working vehicle as set forth in claim 9,wherein said bearing plate is provided with a lubricating oil providingport for leading oil in said transmission housing to a lubricatedportion of said speed-changing system.
 11. A transmission for a workingvehicle as set forth in claim 9, further comprising:a front-wheeldriving PTO unit attached to said transmission housing, and a gear,through which power taken from said speed-changing system is transmittedto said front-wheel driving PTO unit, wherein said gear is disposedadjacent said partition wall in said second chamber.
 12. A transmissionfor a working vehicle as set forth in claim 9, wherein saidspeed-changing system is mechanically combined so that a reversingarrangement and a multi-speed-changing arrangement are provided on aplurality of shafts supported in parallel to one another between saidpartition wall and said bearing plate.
 13. A transmission for a workingvehicle as set forth in claim 12, further comprising:an opening providedin an outer wall of said transmission housing so as to communicate withsaid second chamber; a cover provided so as to cover said opening, and aspeed-changing lever supported by said cover for shifting saidspeed-changing system.
 14. A transmission for a working vehicle as setforth in claim 13, further comprising:a clutch fork supported by saidpartition wall and said bearing plate so as to be longitudinallyslidable according to shifting operation of said speed-changing lever.15. A transmission for a working vehicle as set forth in claim 12,further comprising:an opening provided in a top wall of saidtransmission housing so as to communicate with said second chamber; acover provided so as to cover said opening; a first speed-changing leverfor switching said reversing arrangement, and a second speed-changinglever for switching said multi-speed-changing arrangement, wherein saidfirst and second speed-changing levers are supported by said cover. 16.A transmission for a working vehicle as set forth in claim 15, furthercomprising:a clutch fork supported by said partition wall and saidbearing plate so as to be longitudinally slidable respectively accordingto shifting operation of said first and second speed-changing levers.17. A transmission for a working vehicle comprising:a rear-axle housinghaving a travelling output system disposed therein; a transmissionhousing coupled to said rear-axle housing and interposed between anengine and said rear-axle housing, wherein said transmission housing hasa front end opening and a rear end opening and an interior of saidtransmission housing is divided into a first chamber and a secondchamber through a partition wall; a main-clutch system connected with anoutput portion of said engine, wherein said main-clutch system isinserted into said transmission housing through said front end openingso as to be disposed in said first chamber; a speed-changing system fortransmitting power from said main-clutch system to drive wheels, whereinsaid speed-changing system is inserted into said transmission housingthrough said rear end opening so as to be disposed in said secondchamber; and a bearing plate disposed entirely within said transmissionhousing and said rear-axle housing, said bearing plate forming a rearwall of said transmission housing, wherein said speed-changing system issupported between said partition wall and said bearing plate in saidsecond chamber and a front end of said travelling output system issupported by said bearing plate.
 18. A transmission for a workingvehicle as set forth in claim 17, wherein said bearing plate is providedwith a lubricating oil providing port for leading oil in saidtransmission housing to a lubricated portion of said speed-changingsystem.
 19. A transmission for a working vehicle as set forth in claim17, further comprising:a front-wheel driving PTO unit attached to saidtransmission housing, and a gear, through which power taken from saidspeed-changing system is transmitted to said front-wheel driving PTOunit, wherein said gear is disposed adjacent said partition wall in saidsecond chamber.
 20. A transmission for a working vehicle as set forth inclaim 17, wherein said speed-changing system is mechanically combined sothat a reversing arrangement and a multi-speed-changing arrangement areprovided on a plurality of shafts supported in parallel to one anotherbetween said partition wall and said bearing plate.
 21. A transmissionfor a working vehicle as set forth in claim 20, further comprising:anopening provided in an outer wall of said transmission housing so as tocommunicate with said second chamber; a cover provided so as to coversaid opening, and a speed-changing lever supported by said cover forshifting said speed-changing system.
 22. A transmission for a workingvehicle as set forth in claim 21, further comprising:a clutch forksupported by said partition wall and said bearing plate so as to belongitudinally slidable according to shifting operation of saidspeed-changing lever.
 23. A transmission for a working vehicle as setforth in claim 20, further comprising:an opening provided in a top wallof said transmission housing so as to communicate with said secondchamber; a cover provided so as to cover said opening; a firstspeed-changing lever for switching said reversing arrangement, and asecond speed-changing lever for switching said multi-speed-changingarrangement, wherein said first and second speed-changing levers aresupported by said cover.
 24. A transmission for a working vehicle as setforth in claim 23, further comprising:a clutch fork supported by saidpartition wall and said bearing plate so as to be longitudinallyslidable respectively according to shifting operation of said first andsecond speed-changing levers.
 25. A transmission for a working vehiclecomprising:a rear-axle housing having a travelling output systemdisposed therein; a transmission housing coupled to said rear-axlehousing and interposed between an engine and said rear-axle housing,wherein said transmission housing has a front end opening and a rear endopening and an interior of said transmission housing is divided into afirst chamber and a second chamber through a partition wall; amain-clutch system connected with an output portion of said engine,wherein said main-clutch system is inserted into said transmissionhousing through said front end opening so as to be disposed in saidfirst chamber; a speed-changing system for transmitting power from saidmain-clutch system to drive wheels, wherein said speed-changing systemis inserted into said transmission housing through said rear end openingso as to be disposed in said second chamber; and a bearing plate forminga rear wall of said transmission housing, said bearing plate including alubricating oil providing port for leading oil in said transmissionhousing to a lubricated portion of said speed-changing system, whereinsaid speed-changing system is supported between said partition wall andsaid bearing plate in said second chamber and a front end of saidtravelling output system is supported by said bearing plate.